1. Field of the Invention
The present invention relates to a water base ink for ink-jet recording which avoids any metallic corrosion and elution of nickel from metal members included in a discharge head of an ink-jet recording apparatus and which makes it possible to perform highly accurate printing operation.
2. Description of the Related Art
The printer technique, which is based on the ink-jet recording system, resides in the following printing technique. That is, inks of several basic colors are converted into minute liquid droplets of several picoliters to several tens picoliters, and the minute liquid droplets are selectively landed on the paper so that an image is formed thereby, for example, by means of the bubble system in which the inks are discharged from minute nozzles by using bubbles generated by rapid heating operation, or the piezoelectric system in which the inks are discharged from minute nozzles by using piezoelectric elements which are deformable depending on application of voltage.
The ink-jet recording system has advantages of high printing quality and high printed image quality based on the control of discharge of the minute liquid droplets. An image, which has color reproducibility close to full-color and which has no granular texture, can be formed by highly accurately landing the minute liquid droplets of several picoliters on the paper. However, in order to successfully discharge the minute liquid droplets as described above, it is necessary to adapt a highly accurate technique for controlling the landing of the minute liquid droplets discharged from a sufficiently thin nozzle. In order to highly accurately discharge the ink from such a nozzle having a minute diameter, it is necessary to remove the dust and impurities from the ink. Therefore, it is necessary that the water base ink for ink-jet recording is subjected to precise filtration after preparing the ink. Further, it is necessary that materials, which have no compatibility with the ink and which are sufficiently washed, are used for all parts which make contact with the ink.
Several types of ink-jet recording apparatuses include metal members containing nickel or nickel alloy used for their discharge heads. When the ink is water-based, then the nickel is eluted into the ink as a result of long term contact, and metallic corrosion takes place in some cases. As a result, a problem arises as follows. That is, the metal member is deteriorated due to the elution of nickel and the metallic corrosion as described above, and it is impossible to highly accurately control the discharge and the landing operation.
The present invention has been made in order to solve the problem as described above, an object of which is to provide a water base ink for ink-jet recording which makes it possible to perform stable jetting operation for a long term without causing any deterioration of metal members of a discharge head due to the metallic corrosion and the elution of nickel into the ink and which makes it possible to perform highly reliable and highly accurate recording.
According to a first aspect of the present invention, there is provided an ink-jet printer comprising:
an ink-jet head which has at least a part of ink flow passage formed of nickel or nickel alloy;
ink which contains benzotriazole-based metal-inactivating agent; and
an ink tank which accommodates the ink and which supplies the ink to the ink-jet head.
According to a second aspect of the present invention, there is provided an ink-jet printer comprising:
an ink-jet head which has at least a part of ink flow passage formed of nickel or nickel alloy;
ink which contains alkanolamine; and
an ink tank which accommodates the ink and which supplies the ink to the ink-jet head.
In the printer of the present invention, the ink accommodated in the ink tank contains the benzotriazole-based metal-inactivating agent or alkanolamine. Therefore, the elution into the ink of nickel or nickel alloy which constitutes the ink-jet head is suppressed. Especially, it is possible to suppress the amount of elution of nickel to be not more than 50 ppm. In this specification, the amount of elution of nickel means the amount of elution of nickel obtained when a metal piece (surface area: about 4.5 cm2, weight: about 1 g) is immersed in the ink of about 20 mL followed by being left to stand for 2 weeks under conditions of temperature of 60xc2x0 C. and humidity of 40%.
According to a third aspect of the present invention, there is provided an ink for ink-jet recording comprising:
water;
a coloring agent;
a water-soluble organic solvent; and
a benzotriazole-based metal-inactivating agent and alkanolamine. The present invention will be described in detail below.